Bioluminescence imaging captures the expression and dynamics of endogenous p21 Promoter activity in living mice and intact cells

Abstract

To interrogate endogenous p21WAF1/CIP1 (p21) promoter activity under basal conditions and in response to various forms of stress, knock-in imaging reporter mice in which expression of firefly luciferase (FLuc) was placed under the control of the endogenous p21 promoter within the Cdkn1a gene locus were generated. Bioluminescence imaging (BLI) of p21 promoter activity was performed noninvasively and repetitively in mice and in cells derived from these mice. We demonstrated that expression of FLuc accurately reported endogenous p21 expression at baseline and under conditions of genotoxic stress and that photon flux correlated with mRNA abundance and, therefore, bioluminescence provided a direct readout of p21 promoter activity in vivo. BLI confirmed that p53 was required for activation of the p21 promoter in vivo in response to ionizing radiation. Interestingly, imaging of reporter cells demonstrated that p53 prevents the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway from activating p21 expression when quiescent cells are stimulated with serum to reenter the cell cycle. In addition, low-light BLI identified p21 expression in specific regions of individual organs that had not been observed previously. This inducible p21FLuc knock-in reporter strain will facilitate imaging studies of p53-dependent and -independent stress responses within the physiological context of the whole animal.

HPAN: A BioMed 21 IRC

The Hope Center Program on Protein Aggregation and Neurodegeneration (HPAN) is the most formalized of the Hope Center Research Groups. HPAN, led by Co-Directors Alison Goate and David Holtzman, is one of five Interdisciplinary Research Centers (IRCs) based in the new BJC Institute of Health. This group focuses on the shared mechanism of protein aggregation that underlies numerous neurological disorders. Read more about HPAN....